feat: add a check command

[alexfertel]

This PR introduces a bulloak check command that performs validations on the .tree <> .t.sol files relationship.

[codecov]

Codecov Report

Merging #31 (2d0d73e) into main (a372918) will increase coverage by 2.4%.
The diff coverage is 89.4%.

Additional details and impacted files

Files Changed	Coverage Δ
src/error.rs	81.2% <57.1%> (ø)
src/span.rs	41.8% <62.5%> (ø)
src/check/violation.rs	65.7% <65.7%> (ø)
src/syntax/tokenizer.rs	93.8% <68.4%> (ø)
src/syntax/ast.rs	69.2% <69.2%> (ø)
src/hir/hir.rs	75.0% <75.0%> (ø)
src/scaffold/mod.rs	80.0% <75.0%> (-20.0%)	⬇️
src/syntax/parser.rs	78.9% <77.1%> (ø)
src/check/mod.rs	83.9% <83.9%> (ø)
src/cli.rs	90.0% <85.7%> (+90.0%)	⬆️
... and 9 more